Wafer integrated plasma probe assembly array

ABSTRACT

A wafer integrated plasma diagnostic apparatus for semiconductor wafer processing system having a multiplicity of plasma probe assemblies arranged on a wafer in a planar array fashion such that one plasma probe assembly is in the center and eight more plasma probe assemblies are at intermediate positions such that they lie along the radius from the center to the corners; such corners forming four corners of a square box near the edge of the wafer. At each location and in each of the plasma probe assemblies, there are six possible probe elements having a relative geometrical area such that they are capable of making simultaneous measurements of both spatial resolution and real time measurement of different plasma characteristics at the wafer surface, such as: D.C. potential, A.C. potential, shading induced potentials, ion fluxes, ion energy distribution, and the electron part of the I-V Langmuir probe characteristic.

CROSS REFERENCE To RELATED APPLICATIONS

[0001] This application is a continuation application claiming 35 U.S.C.§ 120 priority from parent U.S. patent application Ser. No. 10/680,791,filed Oct. 6, 2003, entitled “METHODS RELATING TO WAFER INTEGRATEDPLASMA PROBE ASSEMBLY ARRAYS,” which parent Application is hereinincorporated by reference. The parent Application is a Divisionalapplication which claimed 35 U.S.C. § 120 priority from its parent U.S.patent application Ser. No. 09/540,418, filed Mar. 31, 2000, entitled“WAFER INTEGRATED PLASMA PROBE ASSEMBLY ARRAY,” issued Nov. 11, 2003, asU.S. Pat. No. 6,653,852, which Patent is herein incorporated byreference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to plasma diagnosticapparatuses for semiconductor wafer processing systems. Moreparticularly, the present invention relates to a wafer integrated plasmaprobe assembly array.

BACKGROUND OF THE INVENTION

[0003] In the semiconductor industry, plasma, generally comprising ofpartially ionized gas is employed in etching and deposition processeswhereby films are etched from or deposited onto wafer surfaces. In theseprocesses, plasma can be characterized in terms of characteristics ofthe interaction between the surface to be processed and the plasma whichis important in order to control the etch or deposition rate andconsequently, the desired dimension of the etch depth or deposited film.These characteristics include the rate of flow of charged particlesimpinging upon the surface to be processed, the potential distributionof the plasma, the ion current flux, the electron temperature anddensity, and the ion energy.

[0004] In plasma etching systems, knowledge of the potentialdistribution of the plasma is useful because the energy with whichparticles impinge upon the surface to be processed depends upon thepotential distribution. In addition, the plasma potential determines theenergy with which ions strike other surfaces in the chamber. High-energybombardment of these surfaces can cause sputtering and consequentre-deposition of the sputtered material upon the surface to beprocessed. In addition, process uniformity is related to the uniformityof the plasma.

[0005] Similarly, the ion current flux is an important characteristic ofthe plasma generated within a reaction chamber of a semiconductor waferprocessing system. This characteristic generally defines theeffectiveness of the semiconductor wafer processing system.Specifically, the ion current flux affects the uniformity of the etchprocess and indicates potential damage to a wafer. The measurement ofion current at various locations within the chamber is thereforeimportant to characterize the effectiveness of the plasma in processinga wafer.

[0006] It is thus desirable to diagnose instantaneously from outside theprocessing chamber the various characteristics of the interactionbetween the surface to be processed and the plasma. Prior art FIG. 1A isan illustration showing a conventional wafer 1 having probe structures 2formed thereon. The conventional wafer 1 consists of a Si wafer with theprobe structures 2 fabricated using three levels of masks such assubstrate contact, metal pad and oxide layer. The wafer 1 is processedusing conventional wafer manufacturing techniques.

[0007] Prior art FIG. 1B shows the probe structures 2 under greaterdetail. The probe structure 2 includes a semiconductor substrate layer4, which is on the semiconductor wafer 1 on which are comb-likestructures 6 made from metals such as Cu or aluminum and with or withoutlayers of insulators such as oxide layers 8. In the fabrication ofsemiconductor IC's where advanced MOS devices require multiple levels ofmetal interconnections, the size of the comb-like structures is suchthat the height of the structure could be less than 0.5 micron and thespace between the structures could be less than 0.4 micron wide suchthat the aspect ratio could be greater than two. The aspect ratio isdefined as the height of the comb-like structure divided by the width ofthe space between the comb-like structures of prior art FIG. 1B. Thepresence of tall structures on the substrate of a semiconductor wafersometimes causes a differential charging of the surface due to thedifference in electron and ion currents crossing the plasma sheath tothe closely spaced structures.

[0008] The differential charging of the surface (prior art FIG. 1C) ismostly indicative of a non-uniform plasma which includes fluctuations inthe electron and ion densities, and also indicates differences insurface potentials and charge flux densities. If plasma is non-uniformit is anticipated that the depth of etching or the depth of depositionwould be variant across the surface of the wafer. Differential chargingalso could cause oxide damage in semiconductor devices due todifferences in charge flux densities. This is very important as plasmais in contact with smooth and not so smooth surfaces on the wafer.

[0009] It is a purpose of the plasma diagnostics to ensure that theplasma is uniform across the wafer surface so that the differentprocesses taking place in the plasma chamber would result in high yieldfor the device output.

[0010] Prior art FIG. 1C is an illustration showing a probe structure 2on a conventional wafer 1. As shown in prior art FIG. 1C, the presenceof probe structures causes shaded regions 10 where there is chargeaccumulation and unshaded regions 12 where there is no chargeaccumulation. The sign of the charge depends on the surface potential ofthe structure. Local inequality of positive and negative charge fluxesreaching the wafer surface results in a net charge. Local charge-fluximbalances result in circulating currents through the wafer thatgenerate charging damage in gate oxides as in IC process equipment.

[0011] This calls for application of sufficient RF power for better gapfill capability. If the plasma is not uniform across the substrate, thenthe resulting current imbalance causes a voltage to build up in thesubstrate. This voltage allows the current from the plasma to flow inthe substrate to the gate oxides of underlying MOS transistors. However,application of sufficient RF power could cause damage to the gate oxidesleading to gate leakage or oxide breakdown when the amount of currentexceeds the capacity of the gate oxide.

[0012] In general, there are two conventional methods of diagnosing thecharacteristics of interest, a probing method, and an electromagneticwave method. In the probing method, the electrodes 204 usually made frommetal (Prior art FIG. 2A) are on a support 206 are directly introducedinto the plasma 202 to detect the electric current in the plasma whichis then analyzed to determine the characteristics of the plasma. Theprobe is also called the Langmuir probe 200. The characteristic curve250 (Prior art FIG. 2B) is obtained by varying the voltage on theelectrode and measuring the current when the probe or the electrode isplaced in the plasma. The I-V curve 252 indicates that for a largenegative value of the probe potential, all electrons are essentiallyrepelled and only ions contribute to the current leading to an ionsaturation current (Isat). This ion saturation current or Isat simplydetermines the electron density provided electron temperature can bedetermined. Conversely, Isat is also a product of electron charge, disksurface area and ion flow.

[0013] In the electromagnetic wave method, electromagnetic wavesincluding microwaves and lasers interact with the plasma and the resultsof the interaction are detected. By way of example, a beam reflectedfrom the plasma is detected by spectroscopy and analyzed.

[0014] The probing method is limited to probing plasma of relatively lowtemperature and density. For plasmas of electron density Ne on the orderof 10{circumflex over ( )}14 cm-3 and above and electron temperature ofa few tens of electron volts and above, the probing method is of limiteduse. The electromagnetic method suffers from being complex and expensiveto manufacture.

[0015] In view of the prior art that has been done on Langmuir probesand probe structures that are also charge monitors, what is needed is adiagnostic tool capable of taking simultaneous measurements of plasmacharacteristics like uniformity, electron or ion flux densities,potentials and ion energy in real time across a wide area of the wafersurface while the wafer is inside of the plasma chamber.

SUMMARY OF THE INVENTION

[0016] A preferred embodiment of the present invention includes an arrayof electrical probes formed upon an upper surface of a semiconductorwafer. The array of electrical probes provides simultaneous measurementof plasma characteristics in real time across a wide area of the wafersurface. The plasma is diagnosed while in the process chamber to studycharacteristics of the plasma as it interacts with a wafer. The plasmamay be tested, for example, for being homogenous in it's electron or ionflux density, potential and particle temperature.

[0017] The planar array of plasma probes or the planar plasma probeassembly array is connected to the connectors on the wafer through theconductive interconnects. The resultant assembly of probe assemblyarrays, conductive interconnects and the connectors form a waferIntegrated planar plasma probe assembly array. The probe assemblies arepreferably arranged in a pattern: one probe assembly in the center andfour more probe assemblies at intermediate positions such that the fourprobe assemblies lie along the radius from the center to the corners;the corners being the four corners of a square box near the edge of thewafer. On the same wafer are located four optional plasma probeassemblies spaced from the existing probe assemblies such that they lieroughly in between the probe assembly at the center and probe assembliesat the corners of a square. Each probe has six possible probe elements.The probe elements are wafer integrated Langmuir probes. The probeelements are, however, made from low impedance N-type silicon and areexposed to the plasma unlike in prior art where the Langmuir probeelements are conductors.

[0018] The probe elements are clustered into an assembly such that fourof the six probe elements are of intermediate size or medium size,shaped roughly like squares, and are charge monitors with patterning onthem. The structures on the four medium sized probe elements have anon-zero aspect ratio. The four medium sized probe elements are suitablefor patterning in different ways to diagnose potentials due to chargeshading effects. The probe structures on the four medium sized squareelements are rectangular comb-like structures, which don't necessarilyhave identical aspect ratio. An important aspect of having a range ofaspect ratios for the probe elements is that it gives an idea in realtime as to what aspect ratio would cause a wafer damage in real time.The presence of probe structures on probe elements determines chargeaccumulation from the difference in electron and ion currents as theycross the plasma sheath to reach the plasma structures on the wafersubstrate. Such a differential electron or ion flux from non-uniformplasmas is responsible for causing charge induced damage in somesemiconductor devices. The fifth probe element has an area equal to thefour medium sized probe elements and has no patterning on it. An absenceof patterning makes the probe a plain probe. The fifth probe elementwith no patterning is considered to have a zero aspect ratio. The fifthprobe element is considered as a reference Langmuir probe and is exposedto the plasma for measurements of floating potential and saturated ionflux. The sixth probe element is a plain probe with no patterning on it.Again, an absence of patterning constitutes zero aspect ratio. The sixthprobe element is capable of providing electron measurements. However,the sixth probe element is very much smaller than any probe element orexposed substrate for the reason that in order to perform electronmeasurements, the excess current could cause damage to the probe if theprobe's area is bigger because the probes are essentially made ofconductors. The sixth probe element is a novel addition to any of theprior art in plasma diagnostics as it allows electron measurements alongwith flux, potential and charging damage measurements performedsimultaneously in real time.

[0019] While it is important that the geometrical areas of the probeelements be such that the probe elements form a probe assembly, it isnot a requirement that areas of probe pads be the same for all theprobes. The geometrical shapes of the probe elements are also not acritical requirement for the invention. In the invention, the area ofthe smallest probe pad is about 0.25 mm squared while the area of themedium sized probe elements having square pads is 25 square mm each.

[0020] The probe pads, the conductive interconnects and the connectorsare all placed on an N-type silicon wafer. There is also a large areathat is not used for any probing purposes and is exposed to the plasma.These vacant areas on the substrate are covered with a low impedanceN-type silicon for the sole purpose of making an ohmic contact easy. Thelarge area of the wafer substrate also acts a floating referenceelectrode. At the floating potential, the probe collects both thesaturation-ion current as well as canceling electron current such thatthe net current through the probe is zero.

[0021] There are also four more optional plasma probe assembliesarranged in between the center probe assembly and the corner probeassemblies. The four intermediate plasma probe assemblies can be rotatedwith respect to the plasma probe assemblies located already at thecenter and at the corners of the wafer.

[0022] Connections from the probe assemblies on the substrate toconnectors are made on wafer traces. By arranging the connector pads toconform to a standardized mass termination array it is relativelyconvenient to connect them using wire bonds to a flexible circuit jumperstrip to get the signals off of the wafer and into external diagnosticcircuitry which includes an analyzer. The analyzer measures the relativeelectron or ion potentials and current flows from the charge particlefluxes, energies and impressed voltages. The probe assemblies on thewafer surface measure the plasma charge densities and energies when theplasma comes in contact in the plasma processing chamber. The localgrouping of probe array assemblies at nine places allows both spatialresolution and real time measurement of six quantities: DC potential, ACpotential, shading induced potentials, ion fluxes, ion energydistribution, and the electron component of the I-V Langmuir probecharacteristic simultaneously.

[0023] Such an arrangement of planar probe assembly arrays determineselectron or ion flux densities, potentials and ion energy in real timeacross a wide area of the wafer surface while the wafer is inside of theplasma chamber. The probe assemblies on the wafer allows six differentmeasurements on the wafer when the plasma is in the charge shaded regionor when it is in the charge unshaded region.

[0024] In wafer processing, it is highly preferred that the depositionor etching induced by plasma be uniform because millions of devices getbuilt on a single wafer. As there is need to manufacture more number ofdevices on a single large wafer to reduce costs, it is imperative thatthe process involved be as uniform as possible. The diagnostics fromsuch semiconductor equipment should indicate the quality of plasma overa wider area in the semiconductor process chamber because that wouldultimately determine the device quality.

[0025] For a fuller understanding of the nature and advantages of thepresent invention, references should be made to the following detaileddescription taken together with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention, together with further advantages thereof, may bestbe understood by reference to the following description taken inconjunction with the accompanying drawings in which:

[0027] Prior Art FIG. 1(A-C) is an illustration showing a prior artwafer having charge monitors or probe elements formed thereon and waferstructure having plasma shaded and unshaded regions;

[0028] Prior Art FIG. 2(A-B) schematically illustrates a Langmuir probeand the probe's current-voltage characteristic in a prior art;

[0029]FIG. 3 schematically illustrates a plasma chamber with a planarLangmuir probe, in accordance with an embodiment of the presentinvention;

[0030]FIG. 4 is a schematic illustration of a chemical vapor depositionapparatus, in accordance with an embodiment of the present invention;

[0031]FIG. 5 is an illustration of the wafer with planar plasma probeassembly array, in accordance with an embodiment of the presentinvention; and

[0032]FIG. 6(A-C) is a schematic illustration of a plasma probeassembly, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] An invention is disclosed for simultaneous measurement of shadinginduced potentials, ion fluxes, ion energy distribution, and theelectron part of the I-V Langmuir probe characteristic. The presentinvention makes it possible to simultaneously measure several plasmacharacteristics in real time across a wide area of the wafer surfacewhile the semiconductor wafer is inside of the plasma chamber. In thefollowing description, numerous specific details are set forth in orderto provide a thorough understanding of the present invention. It will beapparent, however, to one skilled in the art, that the present inventionmay be practiced without some or all of these specific details. In otherinstances, well known process steps have not been described in detail toavoid obscuring the present invention unnecessarily.

[0034]FIGS. 1 and 2 were described in terms of the prior art. FIG. 3 isan illustration of a planar Langmuir probe 300 in accordance with oneembodiment of the present invention. In this embodiment, the presentinvention makes use of a “Planar Langmuir Probe”. The Planar LangmuirProbe 300 includes an enclosure 302, a disc shaped electrode 304 on awafer support 306. The disc shaped electrode 304 is positioned next tothe wall of the enclosure 302. Preferably, the disc shaped electrode 304has a relatively large surface area S (for example, a few square cm).The electrode 304 further includes a rear surface directed to the wallcoated with an insulating material. The forward contact of the Langmuirprobe is a conductor, and when placed in direct contact with movingcharged particles found in plasma, a current is created through thewiring in the Langmuir probe. The apparatus of FIG. 3. is specificallyfor diagnostics of the plasma and so the enclosure 302 is preferably avacuum enclosure that is filled with low pressure gas, such as Argon.Applying a bias voltage to the wafer support 306 generates plasma. Toincrease the ion impact power on the surface of the sample placed on theelectrode 304, a radio frequency (RF) generator 308 is connected to thewafer support 306. An analyzer 310 connected to the plasma supportmeasures the voltage across the disc shaped electrode 304.

[0035] While in the Langmuir probe method, a cylindrical probe made ofconductor is placed in the plasma and the current is measured when avoltage is applied between the probe and the enclosure walls. In thepresent invention, a planar Langmuir probe made from low impedanceN-type Silicon is employed to determine the plasma characteristics. Thesource for plasma could be d.c. voltage source, an electrode supplied bya radio frequency generator, an inductive coupling radio frequencysource or a microwave source. The purpose of the RF Generator is toincrease the ion impact power on the surface of the processing waferwhen the plasma is impinging inside the plasma chamber. FIG. 4 is anillustration of a plasma processing system such as a high density plasmainduced chemical vapor deposition process system 400 where theinteractions of the plasma with the wafer is done from inside theprocessing chamber. In such a system, the plasma probes are embedded onthe wafer itself and characteristics of the plasma are determined sincethe same plasma would interact with wafers during deposition or etchingas applicable. The process system 400 includes a substrate 304positioned on a chuck or a wafer support system 306, a turbo molecularpump 310, a wave guide 312, large magnets 314 surrounding a sourcechamber 316, outer magnets 318, and inner magnets 320.

[0036] In operation, the substrate 304 rests on the chuck 306 disposedinside a plasma chamber and biased by a RF generator 308. The chuck maybe either an electrostatic chuck or a mechanical chuck and may be biasedby a RF generator 308. A turbo molecular pump 310 controls the flow ofhydrogen inside the plasma chamber. A wave guide 312 brings microwaveinside source chamber 316, which is located above the plasma chamber.Large magnets 314 surrounding the source chamber generate a magneticfield that sets up a resonance zone inside the source chamber, where theelectrons gyrate at the frequency of the incoming electromagnetic waveor microwave. As a result, a plasma is generated and spreads into theplasma chamber and onto the substrate 304. Outer magnets 318 and innermagnets 320 are used to fine focus this plasma.

[0037] In order to perform diagnostics in the plasma chamber of achemical vapor deposition system 400, the wafer containing the planararray of probes is introduced into the chamber. Plasma is generated in away similar to what is described above. The forward contact of theLangmuir probes is a conductor, and when placed in direct contact withmoving charged particles found in plasma, a current is created throughthe wiring in the Langmuir probe. The enclosure is preferably a vacuumenclosure that is filled with low pressure gas, such as Argon. Applyinga bias voltage to the wafer chuck or wafer support 306 generates plasma.To increase the ion impact power on the surface of the sample placed onthe electrode 304, a radio frequency (RF) generator 308 is connected tothe wafer support 306. The plasma characteristic, such as, prior artFIG. 2B is obtained by varying the voltage on the probe and measuringthe current when the probe is placed in the plasma. For large negativevalues of the probe potential, all electrons are essentially repelledand only ions contribute to current leading to an ion saturation current(Isat). This ion saturation current or Isat simply determines theelectron density provided electron temperature can be determined.Conversely, Isat is also a product of electron charge, disk surface areaand ion flow. For a more detailed account of measurement of electron andion parametrics, one can refer to “Electric Probes for PlasmaDiagnostics” by Swift and Schwar (1971) which is incorporated herein byreference in its entirety.

[0038]FIG. 5 is an illustration showing a planar plasma probe assemblyarray 600, in accordance with an embodiment of the present invention.The plasma probe assembly 600 in FIG. 5 includes six probe elements(633, 635, 637, 639, 641, and 643). Four of the six probe elements (635,637, 639, and 641) are medium sized probe elements (FIG. 6B) suitablefor patterning in different ways to diagnose potentials due to chargeshading effects. The probe is usually on a substrate 660 on which thereis probe having a layer of overcoat 658 and metal 656. The medium sizedprobe elements are roughly in the shape of a square but the shape itselfis not so important.

[0039] As in prior art shown in FIG. 1B, the probe elements withpatterning include structures 2 that are integrated with a non-zeroaspect ratio. The difference in the isotropy of electron and ioncurrents crossing the plasma sheath to closely spaced probe structureson the wafer substrate causes differential charging. Presence ofcomb-like structures causes shaded regions 10 (Prior art FIG. 1C) wherethere is charge accumulation and unshaded regions 12 (Prior art FIG. 1C)where there is no charge accumulation. If the plasma is not uniformacross the substrate, then the resulting current imbalance causes avoltage to build up in the substrate. This is understood in the priorart to be the source of charge induced damage. The medium sized probeelements (635, 637,639, and 641 in FIG. 6B) in the invention,essentially, determine the charge uniformity of the plasma at the bottomof the structures in the processing chamber. The fifth probe element 633(FIG. 6C) has an area equal to the four medium sized probe elements(635, 637, 639, and 641 in FIG. 6A) and constitutes a large probeelement that is exposed to the plasma for floating potential andsaturated ion flux measurements. The fifth probe element consists of asubstrate 666 coated with a layer of overcoat 664 on which is a metalconductor 662. The fifth probe element is plain meaning it doesn't havepatterning on it. That constitutes an aspect ratio of zero for plainprobe elements. The sixth probe element 643 is a small probe, but withan area of the probe element about 1% the probe element area of all thesix elements combined. The sixth probe element 643 is capable ofproviding electron measurements. The sixth probe element is on a wafersubstrate 654 with a layer of overcoat 652 on which is the conductorelement 650 which acts as a probe. The sixth probe element has nopatterning of structures and has an aspect ratio of zero.

[0040] From the above it will be appreciated that the describedembodiments provide a plasma diagnostic tool capable of simultaneouslymeasuring six different plasma characteristics on a large wafer area.

[0041] While the invention has been described in terms of preferredembodiments, other embodiments, including alternatives, modifications,permutations and equivalents of the embodiments described herein, willbe apparent to those skilled in the art from consideration of thespecification, study of the Figures, and practice of the disclosedembodiments. Therefore, the embodiments and preferred features describedabove should be considered exemplary, with the invention being definedby the appended claims, which therefore include all such alternatives,modifications, permutations and equivalents as fall within the truespirit and scope of the present invention.

What is claimed is:
 1. A wafer integrated plasma probe assembly arraycomprising: a plurality of plasma probes; the plurality of plasma probescomprising: a larger sized probe; four medium sized probes; and asmaller sized probe; wherein the larger sized probe has a geometricalarea equal to the geometric area of the four medium sized probes; andthe smaller probe has an area which is very much smaller than any of thelarger and medium sized probes.
 2. A wafer integrated plasma probeassembly array as in claim 1 wherein all of the plasma probes areLangmuir probes made from low impedance N-type Silicon.
 3. A waferintegrated plasma probe assembly array as in claim 1, the plurality ofplasma probes further comprising the larger sized probe and the smallersized probe being plain probes.
 4. A wafer integrated plasma probeassembly array as in claim 1, the plurality of plasma probes furthercomprising the four medium sized probes being patterned probes.
 5. Awafer integrated plasma probe assembly array of claim 1, wherein thesmaller sized probe has a geometrical area of about 0.25 mm squared. 6.A wafer integrated plasma probe assembly array as in claim 4, whereinthe patterning on the four medium sized probes constitutes fourdifferent aspect ratios.
 7. A wafer integrated plasma probe assemblyarray as in claim 1, wherein the smaller sized probe has a probe elementarea of about one (1%) percent of the geometrical area of all the largersized probe and the four medium sized probes and the smaller sized probecombined.
 8. A wafer integrated plasma probe assembly array comprising:a plurality of plasma probes; the plurality of plasma probes comprising:a larger sized probe having a probe element area; four medium sizedprobes each having a probe element area; and a smaller sized probehaving a probe element area; wherein the probe element area of thelarger sized probe is about equal to the combined probe element area ofthe four medium sized probes; and the probe element area of the smallerprobe is very much smaller than the probe element area any of the largerand medium sized probes.
 9. A wafer integrated plasma probe assemblyarray as in claim 8, wherein the probe element area of the smaller sizedprobe is about 0.25 mm squared.
 10. A wafer integrated plasma probeassembly array as in claim 8, wherein the probe element area of thesmaller sized probe is about one (1%) percent of the respective probeelement area of all the larger sized probe and the four medium sizedprobes and the smaller sized probe combined.
 11. A wafer integratedplasma probe assembly array as in claim 9 wherein all of the plasmaprobes are Langmuir probes made from low impedance N-type Silicon.
 12. Awafer integrated plasma probe assembly array as in claim 10, wherein allof the plasma probes are Langmuir probes made from low impedance N-typeSilicon.
 13. A wafer integrated plasma probe assembly array as in claim9, the plurality of plasma probes further comprising the larger sizedprobe and the smaller sized probe being plain probes.
 14. A waferintegrated plasma probe assembly array as in claim 10, the plurality ofplasma probes further comprising the larger sized probe and the smallersized probe being plain probes.
 15. A wafer integrated plasma probeassembly array as in claim 9, the plurality of plasma probes furthercomprising the four medium sized probes being patterned probes.
 16. Awafer integrated plasma probe assembly array as in claim 10, theplurality of plasma probes further comprising the four medium sizedprobes being patterned probes.
 17. A wafer integrated plasma probeassembly array comprising: a plurality of plasma probes; the pluralityof plasma probes comprising: a larger sized probe; four medium sizedprobes; and a smaller sized probe; wherein the larger sized probe has aprobe element area equal to the probe element area of the four mediumsized probes; wherein the smaller sized probe has a probe element areaof about one (1%) percent of the probe element area of all the largersized probe and the four medium sized probes and the smaller sized probecombined.
 18. A wafer integrated plasma probe assembly array as in claim17 wherein all of the plasma probes are Langmuir probes made from lowimpedance N-type Silicon.
 19. A wafer integrated plasma probe assemblyarray as in claim 17, the plurality of plasma probes further comprisingthe four medium sized probes being patterned probes.
 20. A waferintegrated plasma probe assembly array as in claim 17, the plurality ofplasma probes further comprising the larger sized probe and the smallersized probe being plain probes.